1. Field of the Invention
The present invention relates mainly to a foldable element for use in a case for a roll of photosensitive material, in particular for graphic arts film. The invention relates also to a support means obtained from the foldable element for holding the roll in the case, and to a spacer also obtained from the foldable element for filling free space in the case between the case itself and support elements.
Photosensitive material for professional use such as graphic arts is supplied in the form of rolls, in which a photosensitive film is wound onto a cylindrical core. The roll is protected by an outer wrapping of a light-tight film and by placing it into a case.
Within the case, the roll is supported in a suspended condition because any direct contact against the walls of the case may damage the light-tight wrapping and hence the photosensitive material. Therefore, the roll is supported by two support elements, having a plate with a central protrusion which is inserted into the core.
The diameter of the core and of the roll is standardized, while the length may vary within a certain range. It is not a problem to have cores of many different lengths, but it is expensive to keep stocks of cases of many different diameters.
Therefore, it is normal practice to keep on stock cases of few sizes, and so to place in a case of a certain size rolls having different length. The free space left between one of the support elements and the internal wall of the case is filled with spacers.
The problem at the basis of this invention is to provide an element which can be used both to support the roll and to fill the free space.
This problem is solved, according to the invention, by a foldable element, characterized by comprising a flat base, a folding area dividing the base into a first and a second portions, a first and a second flaps formed in the first and second portions respectively by means of respective first and second cutting lines and first and second folding segments, the first and second folding segments forming angles of 70.degree.-110.degree. and passing through respective first and second reference points symmetrically positioned on the first and second portions with respect to the folding area, a first slit opened in the first flap along a line passing through the first reference point and perpendicular to the first folding segment, a second slit opened in the second flap along a line passing through the second reference point and perpendicular to the second folding segment, a third slit opened in the second portion of the base along a line passing through the second reference point and parallel to the first folding segment, the second and the third slits being adjacent and open one to the other at the second reference point, the first slit intersecting the first cutting line but not the first folding segment, the second slit not intersecting the second cutting line. This element can be used to obtain a support means by bending, along the first folding segment, the first flap by 90.degree. on a side of the base; bending, along the second folding segment, the second flap by 90.degree. on the other side of the: base; bending the base by 180.degree. along the folding area while simultaneously inserting the first flap into the second and third slits and matching the first slit around the second flap.
With ther term "inserting" it is meant to act on a flap by moving it into a slit, so that the thickness of the flap is clamped (with or without: clearance) by the sidewalls of the slit. With the term "matching" it is meant the reciprocal action, i.e., to act on a slit by moving it towards a flap, so that the thickness of the flap is clamped (with or without clearance) by the sidewalls of the slit.
The same element can be used to obtain a spacer by bending the base by 180.degree. along the folding area, without bending any of the first and second flaps.
It is clear that the first and second reference points are not physical entities but just virtual elements, used to better define the invention. When the foldable element is used to make a support means, the reference points are effectively placed (with a certain approximation) on the axis of the roll to be suspended. Such points are thus preferably in barycentric positions on the respective first and second portions of the base. A different position would be acceptable in respect of protection, but would cause a waste of space inside the case, being the roll cylindrical; besides, an asymmetric position would require extra care in assembling the whole package, in order to place the support means in the right position.
Preferably, the first and second folding segments are perpendicular one to the other, and more preferably equal one to the other, apart from the slits opened therein. This ensures that the protrusion obtained by the two flaps in the support means fits symmetrically the cylindrical core of the roll, because the two flaps are perpendicular one to the other. The roll is fully suspended not only in vertical direction but also in horizontal direction; in the event of shocks or overturning while transporting the case, there is no risk of contact between the roll and the case.
The folding area can be obtained in many different ways. For example, it may consist of a single folding line, or of two parallel folding lines. The former alternative is preferred for its simplicity when the thickness of the material is not too great; for thicker materials, the latter alternative is preferred.
The base can be made of any suitable sheet material. However, it is preferred to make it with cardboard. This material is very cheap, can be easily cut and folded, and has a strength sufficient for the intended use. Moreover, cardboard can be recycled, thus contributing to the protection of the environment. In this respect, it must be noted that also the case can be (and normally is) made of cardboard; therefore, the packaging of the roll may be completely made of the same recyclable material, giving the user the opportunity of easily disposing it in an environmentally friendly way.